1. Field of the Invention
The present invention relates generally to semiconductor wafer preparation and, more particularly, to the cleaning and drying of a semiconductor substrate using space- and process efficient spin, rinse, and dry (SRD) modules.
2. Description of the Related Art
Wafer preparation and cleaning operations are performed in the fabrication of semiconductor devices. One common wafer preparation operation dispersely repeated during substrate preparation is a spin rinse and dry operation using a spin, rinse, and dry (SRD) module. Typically, the spin, rinse, and dry operations are performed in a bowl mounted on an SRD housing, which in turn is secured to a spindle. Typically, a motor causes the spindle, a chuck mounted on the spindle, and the wafer held by spindle fingers attached to the chuck to rotate. Generally, to receive the wafer to be prepared, the spindle fingers move upwardly within the bowl such that they extend outside the bowl and above the wafer processing plane. At this point, an end effector delivers the wafer to be processed to the spindle fingers. Subsequent to receiving the wafer, the spindle fingers and the wafer attached thereto move back down and into the bowl, thus placing the wafer at the level of wafer processing plane.
Generally, the wafer is rinsed by applying de-ionized (DI) water onto the surface of the wafer through a spigot, as the wafer is spun at high revolutions per minute (RPMs). Once the rinsing operation has concluded, the supplying of DI water is stopped by turning off the spigot, and then wafer is dried as the wafer is continuously spun at high RPMs. As soon as the drying operation has completed, for a second time, the chuck, the spindle fingers, and the wafer are moved out of the bowl and above the wafer process plane. At this time, an end effector reaches in and removes the wafer from the SRD module.
Several limitations are associated with the conventional SRD modules. Primarily, in the typical SRD modules, the wafers are processed in the horizontal orientation. Consequently, to achieve a wafer surface free of contaminants, the wafer must be spun for a significant period of time at high RPMs, thus increasing the spin, rinse, and dry cycle per wafer. As can be appreciated, this reduces the overall throughput of the SRD module.
A second limitation is the disposing of the heavy and large chuck assembly as well as the large motor required to drive the chuck assembly inside the SRD module. A third limitation is the use of an enormous frame support to accommodate the multiplicity of forces created by the spinning of the wafer at high RPMs for an extended period. As a combined effect of these two limitations, the conventional SRD modules have significantly large frames and frame supports, thus unnecessarily occupying a significantly large valuable clean room space.
Additionally, besides unnecessarily occupying valuable space, the chuck assemblies have extremely complex designs. For instance, the chuck assemblies are designed to rotate and move up and down within the bowl so as to receive or deliver the wafer. As a result, the movement of the chuck assembly within the bowl mandates that the chuck remain properly calibrated so that it comes to rest at the exact process level. In the situations the chuck is not aligned properly, the chuck assembly must be realigned. This process is very time consuming and labor intensive, and it requires that the SRD module be taken off-line for an extended period of time, thus reducing throughput.
In addition to needing realigned constantly, the chuck assemblies perform unnecessary movements to load and unload the wafers to and from the spindle fingers. By way of example, in conventional SRD modules, the loading of the wafer onto the spindle fingers involves four stages. First, to receive a wafer, the chuck and the spindles are moved out of the bowl, such that the spindles are positioned above the wafer process plane. As a result, to deliver the unprocessed wafer to the edges of the spindle fingers, the end effector holding the wafer is first moved horizontally over the bowl at a level that is above the horizontal plane of the spindle fingers (which are already in the up position). Thereafter, the end effector must move downwardly (while over the bowl) until the wafer reaches the level of the spindle finger at which point the spindle fingers can engage the wafer. Once the spindle fingers have engaged the wafer, the end effector relinquishes the wafer and thus physically delivering the unprocessed wafer to the spindle fingers. Finally, to pull out, the end effector is required to move slightly down and away from the wafer before moving horizontally away from over the bowl. Each of the up and down movements of the end effector is performed using the xe2x80x9cZxe2x80x9d speed of the end effector, which in fact is a significantly low speed. As a result, in each spin, rinse, and dry cycle, a significant amount of time is spent merely to load and unload the wafer. Hence increasing the SRD cycle per wafer, which in turn reduces the overall throughput of the SRD module.
In view of the foregoing, a need therefore exists in the art for a spin, rinse, and dry module that occupies less clean room space and produces higher throughput while efficiently improves the spin, rinse, and dry operations performed on the surfaces of the substrates.
Broadly speaking, the present invention fills these needs by a spin, rinse, and dry (SRD) module and methods for implementing the same that efficiently optimize the spin, rinse, and dry operations performed on the surfaces of the substrates. The SRD module of the present invention occupies less clean room space while producing higher throughput. Preferably, the SRD module of the present invention implements a pair of drive rollers and an engaging roller to engage the substrate during the spin, rinse and dry operations. The pair of drive rollers and the engaging roller are disposed within the SRD module such that while the rollers engage the substrate during the spin, rinse, and dry operations, a plane containing the substrate, herein defined as a process plane, creates a process angle with the horizontal plane. In preferred examples, the drive rollers are configured to spin the engaged substrate while the engaging roller is configured to be retractable so as to create a clear path for the loading and unloading of the substrate.
It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a method for processing a substrate in a spin, rinse, and dry (SRD) module is disclosed. The method includes providing the substrate to be processed, positioning the SRD module in a substrate receive position, and orienting the substrate to be processed at an insert position that is defined at an angle. The method further includes inserting the substrate into the SRD module at the angle, and placing the SRD module in a process position. Also included is spinning the substrate at the angle, and rinsing and drying the substrate being spun at the angle.
In another embodiment, a method for processing a wafer in a spin, rinse, and dry (SRD) module is disclosed. The method includes engaging a wafer in a process plane, and spinning the wafer in the process plane. The process plane is configured to define a process angle with a horizontal plane configured to optimize the performance of the SRD module. The method further includes cleaning a top surface and a bottom surface of the wafer while spinning the wafer in the process plane.
In yet another embodiment, a method for processing a wafer in a spin, rinse, and dry (SRD) module is disclosed. The method includes engaging a wafer in a process plane, spinning the wafer in the process plane, and cleaning a top surface and a bottom surface of the wafer while spinning the wafer in the process plane. The process plane is configured to define a process angle with a horizontal plane designed to optimize the performance of the SRD module. The cleaning a top surface and the bottom surface of the wafer is designed to include rinsing the top surface and the bottom surface of the wafer with DI water while spinning the wafer in the process plane. The cleaning a top surface and the bottom surface of the wafer further includes applying a megasonic flow to the top surface and the bottom surface of the wafer while spinning the wafer in the process plane.
In still a further embodiment, a method for processing a wafer in a spin, rinse, and dry (SRD) module is provided. The method includes engaging and spinning a wafer in a process plane. The process plane is configured to define a process angle with the horizontal plane designed to optimize a drying of the wafer. The method further includes cleaning and drying a top surface and a bottom surface of the wafer while spinning the wafer in the process plane.
In still a further embodiment, a wafer preparation module is disclosed. The wafer preparation module includes an enclosure, which contains wafer engaging rollers. The wafer engaging rollers are oriented at an angle and are designed to spin a wafer at an angle during preparation.
In still another embodiment, a spin, rinse, and dry (SRD) module is disclosed. The SRD module includes an enclosure, a pair of driver rollers, and an engaging roller. The enclosure has an outer wall that includes a window therein. The window is defined within the outer wall so as to create a process angle with a horizontal plane. The pair of drive rollers is defined within the enclosure and are configured to spin a substrate to be processed while engaging the substrate to be processed. The engaging roller is defined within the enclosure and is configured to engage the substrate to be processed. The engaging roller and the pair of drive rollers are configured to engage the substrate to be processed such that the substrate to be processed creates an angle with the horizontal plane that is substantially equivalent to the process angle.
The advantages of the present invention are numerous. Most notably, unlike conventional SRD modules, the angular SRD module of the present invention implements rollers to engage and spin the substrate to be processed at a process/insert angle configured to optimize the drying of the surfaces of the substrate. In this manner, the number of movements required to load and unload the wafers are decreased, reducing the time for each spin, rinse, and dry cycle, thus increasing throughput. Another benefit is the implementation of rollers rather than the spindle fingers and chuck. That is, by implementing rollers to engage the wafer, the angular SRD module of the present invention ensures the cleaning of the whole wafer, i.e., both, top and bottom surfaces of the wafer. Yet another benefit is that due to the wafer being engaged at an angle, less mechanical movements are necessary to process the wafer, thus the wafer can be processed using non-destructive low to high RPMs.
Still another benefit of the present invention is that by using rollers rather than the chucks and spindle fingers, the angular SRD module 100 of the present invention is smaller than the current SRD modules, thus occupying less clean room space. Still a further benefit of the present invention is employing improved drying methods. That is, as a result of using the combined effects of the dry assist mechanism, the processing of the wafer at an angle, and using highly evaporative solvents to clean the wafer, the drying operation of the present invention is significantly enhanced. For example, the present invention efficiently dries a wafer while it ensures edge cleanliness. As a result, the drying cycle of the SRD module is reduced, thus increasing the throughput. Ultimately, the angular SRD module achieves a drier wafer implementing low non-destructive RPMs.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.